An apparatus and a method for determining characteristics of earth formations traversed by a borehole that compensates the mudcake and standoff effects with fewer than usual detectors. The apparatus includes an radiation source effective to generate first and, spatially as well as temporally separate, second X-rays for irradiating earth formations from first and second entrance angles, one or more X-ray detectors capable of generating a first and a second signal indicative of the intensity of the first and second X-rays returned from earth formations to the detectors and a housing accommodating the radiation source and the detectors.